CXCR4 signaling and MB cell migration is inhibited by GRK6. (A) D556 or Daoy was transfected with control siRNA or GRK6 siRNA. The cells were starved for 24 h after transfection and then stimulated by 100 ng/ml CXCL12 (SDF-1α) for 15 min. The results show that down-regulation of GRK6 causes increased CXCL12-induced P-ERK in both cell lines. (B) Daoy was transfected with control siRNA or GRK6 siRNA and then starved for 24 h prior to examination by Boyden chamber migration assay. Results show serum-mediated migration is significantly increased in the cells transfected with GRK6 siRNA (P < 0.01).